Electric fuse



Oct. 29, 1940. 5, KLElN 2,220,058

ELEGTRI C FUSE Filed May 6, 1937 mmvron Patented Oct. 29, 1940 UNITEDSTATES PATENT OFFICE 13Chims.

This invention relates to fuses for the protection of electric wiringandapparatus, and relates particularly to enclosed fuses and fuse links.The object is to provide an enclosed fuse by an economical combinationand arrangement of convenient and improved parts having particularlywell secured electrical connections of the fusible link, said partshaving an economical tortuous vent for a fuse cartridge, and havingmeans for interlocking the parts of a fuse against unintentionalloosening; and either or all of the aforesaid in an irreducible numberof parts.

Fuses of the renewable cartridge type, generally include from five tofifteen separable parts plus the fuse link to arrange in properalignment, when renewing a fuse link. This improved fuse includes onlythree separable parts plus the fuse link.

The type of contact used in many renewable fuses, is such that one canonly assume there is a good connection with the fuse link, and that agood connection will remain so. In this improved fuse there is anunusually positive connection between the fuse link and the terminals ofthe fuse case, which is obvious as the fuse case and the fuse link are.assembled, and means are provided to interlock the assembled fuse forsafekeeping, other improvements also are disclosed, all with the objectof providing a more satisfactory enclosed fuse, which is attained asdescribed and as illustrated in the. accompanying drawing, where,

Fig. 1 is a view of an improved fuse partly sec- F tional.

Fig. 2 is another view of the fuse shown at Fig. 1, but without the fusecase terminals, showing one terminal of the fuse link disconnected, andthe channels to vent the fuse combustion chamber.

Fig. 3 is a view of an improved fuse link.

Fig. 4 is an enlarged view of an improvedfuse for small fuse links, thiscase is broken in two parts to show opposite sides of the ends of thecase, at one end is the disconnected terminal of a small fuse link whichwas smooth before being connected.

Referring in detail to the accompanying drawing, the number N indicatesa nonconducting tubular casing composed of vulcanized fiber, number l2indicates a removable fuse link enclosed in the casing ll, tubular metalferrules I3 and I! are riveted H or otherwise fixed on the ends of thecasing II which including ferrules is fully clear throughout, theferrules l3 each have an external screw thread I! near that edge of theferrule which is on the casing, and the remainder of each ferrule I3toward the outer edge has the shape of a cone frustum I! or is conicalin shape II, the ferrules it each have a longitudinally extendingdepressed space, chase, or path, formed by reducing the screw thread It,which I hereinafter term a groove I1 in the external surface of theferrule, interrupting the screw thread l6, and the groove I1 continueson and into the case Ii for a very short distance. This groove serves tohold the fuse link against rotary displacement from abrasivelyestablished electrical connections.

Tubular metal caps I8 and ll comprise the terminals of the fuse case ll,each cap having a conical formation It on the inside walls toward theclosed part of the cap it, this conical formation I! corresponds to theconical formation II of the ferrules l3, and the remainder of the insidewalls toward the opening of each cap it is occupied by an internal screwthread 20 having blunt edges 2| to obviate the destructive cutting ofsharp edges, because the threads 20 must make a strong abrasive contactwith the terminals of a fuse link. The caps 18 each have a rectangularindentation 22 in the edge of the rim. It is to be understood that theexternal contact surface for the caps I0 is not to be limited to anyparticular type of fuse connection in a cutout block or fuse panel, forexample, at Fig. 1,

' blade contacts are shown at 25, and at Fig. 3, the

contact surface is of the ferrule type.

It is to be noted that this fuse case consists of only three parts, eachpart substantial and rigid throughout, and the tubular casing fullyclear throughout.

A vent for heat and expanding gas is formed in each end of the fuse caseH, by parallel longitudinally extending open grooves or channels 23 and24, in the external screw thread l5, and each'channel crosses all butone or two turns of the screw thread, each channel having one end openand one end blocked by unchanneled turns of the screw thread, thechannel 23 having one end opening in the combustion chamber of the fusecase, the channel 24 having one end open to the outside of the fuse caseand a plurality of such channels would alternate in this manner. Eachcap is has a blunt edged internal screw v thread 20 which incompletelynlls the hollows between turns of the screw thread i5, therefore, when acap I 8 is in place on the end of the case II, the channels 2! and 24are covered and connected by lateral channels formed by the engagementof incomplete screw threads, and gas can escape through a tortuousnetwork of indirect connecting channels.-

In Fig. 1, one of the above mentioned lateral channels is indicated bythe number 2|, and it is to be noted that there are four of thosechannels in a row, and the diameter of each lateral channel is such asto restrict the passage of flame, yet

the aggregate oflateral passage for gas is about equal to the passagefor gas through either of the relatively larger longitudinal passages 23or 24.

This arrangement permits expanding gas to be vented copiously, therebymaterially promoting the extinguishment of an arc when the fuse blows,

5 by promptly dispersing the metallic vapor through which an arc ismaintained.

It should be recalled that an object of this invention is a particularlywell secured electrical connection of the fuse link, and notice that thesame is attained by electrically connecting each electrical terminal ofthe link by a gripping contact with said internal thread of the caps I8and by again gripping each terminal between the corresponding conicalsurfaces I6 and I9. Either of these contacts are good electricalconnections, but. by using both of these means for contact, aparticularly eflicient electrical connection of the link is secured, theimportance of which is scarcely to be belittled; and furthermore, whileit is desired to prevent the use of fuse links having a capacity whichis excessive for the cartridge,

it is harmless and frequently expedient to use links having a lowercapacity and relatively thin electrical terminals which cannot beproperly 28 gripped by the internal threads of the-caps I8,

but which will be properly gripped by the corresponding conical surfacesI6 and I9 while the grooves at I1 hold such thin terminals in position.

At Figs. 1 and 2, the caps I8 have the common 80 knife blade type ofcontact, but in this improved fuse the blade 25 and the terminal cap I8are inseparable or made in one piece.

The fuse link I2 has the more fusible portion in the middle, and theterminals '26 and 26 which 38 are the electrical terminals of the link,being of insumcient pliability, are each provided with a multiple ofparallel ridges and hollows 21 forming the segment 21 of a screw thread,these segments do not precisely correspond to a, screw thread and whenengaged as such, will be slightly deformed by abrasion in the making ofa good electrical connection, each terminal of the fuse link I2 has asupplemental portion 28 at the very end, and each portion bears marks 29identifying 45 the electrical capacity of the fuse link. The terminals26 .are relatively flat yet slightly curved to suit the curved form ofthe terminal caps I8 and the ferrules I3, and it is to be noted thatthese improved fuse links are essentially of extra 60 length.

Fuse links of each electrical capacity, will have terminals preciselycorresponding in proportions to the groove I! in appropriate fuse caseswhen the caps I8 are in place, to prevent overfusing 55 exceptwith muchdifficulty, it is to be noted that this' arrangement makes itimpractical to use the groove I! for venting gas, which is not desirablein that it would foul the electrical contacts, hence the vents hereindescribed, but in every 00 instance the fuse link terminals will beproportioned for adequate electrical contacts, and for restricting thefusibility of the link to the combustion chamber, as illustrated.

To install the fuse link I2 in the fuse case II,

65 the straight fuse link is inserted inthe casing and each terminal 26bent like a hook, to engage the groove I! in each end of the fusecasing, and

' that portion of each terminal which is like the segment 21 of ascrewthread, is held in posi- 70 tion to complete the external screw threadI5, where said screw thread is interrupted by the groove l1, then thecaps I6 and I8 are screwed on both the fuse link terminals and theferrules I3 and I3 of the fuse casing, thereupon 75 the internal screwthread of each terminal cap engages the corresponding ridges and hollowsof each segment 21, thereby gripping the fuse terminals, and a portion3| of each fuse terminal 26 is again gripped by,the conical surface I6of each ferrule I3 with the cooperating conical sur- 5 face I9 of eachcap I8, thereby abrasively establishing an exceptionally positiveelectrical connection of the link. In renewing these fuses, no

the case II and back against the external side of each caps, engagingeach indentation 22 and revealing the marks 29 and 29 which identify theenclosed fuse link, thereby locking the assem- 20 bled fuse againstunintentional loosening.

It is to be noted that in each cap I8, the indentation 22 is located foraligning and locking terminal blades in proper position.

It should be noted that the groove II at each 25 end of the fuse case,is on an opposite side of the case II, and the fuse terminals 26 areformed accordingly, therefore the fuse link I2 must take a diagonalposition in the fuse case with the most fusible portion in the center ofthe com- 30 bustion chamber.

i The renewable fuse shown in Fig. 4, is a modification of the fuse atFig. 1, and Fig. 2, and is intended for fuses of small capacity, smallflat fuse links are composed of soft pliable material, 8 therefore insome of the new fuse links, the screw thread segment 21 is omitted, butthe fuse terminal 26 will have the essential length, curved surface andsupplemental portion 28, and an excellent contact is made with theterminals of 40 the fuse case by the blunt internal screw thread 20 ofeach cap I8 impressing and engaging correlative ridges and hollows inthe normally smooth and pliable fuse link terminals, as the cap I8 isscrewed on both the soft fuse terminal and the ferrule I3 on each end ofthe fuse case, and to make this grip better, the groove I! at each endof the fuse case II, at Fig. 4, is formed by having reduced screwthreads as at 32 in the groove II, thereby providing a serrated bottomin the groove, which cooperates with blunt internal screw thread 20 indeforming and gripping the fuse link terminals 26.

This improved fuse provides, in three simple parts, simple connections,automatically scraped clean, electrically positive, and'eifectivelylocked.

The fuse links are renewed easily and with confidence. The fusesemploying blade contacts are rigid in comparison with prior'fuses. Thecom- 'bustion chamber is easy to clean. The contacts 0 Y 1. A renewablecartridge fuse comprising, in

combination, a tubular casing having threaded ends and shallow fusereceiving channels extending across the threads, a threaded metal cap oneach threaded end, and, extending through [5 the tubular casing, a. fuselink the ends of which constitute electrical terminals and are securedin said shallow channels by being gripped between the threaded faces ofthe threaded ends of the tubular casing and the threaded faces of themetal caps to provide electrical contact between the caps and the fuselink.

2. A renewable cartridge fuse consisting of a tubular casing, a fuselink having a central fusible portion extending diagonallylongitudinally through the tubular casing to position the centralfusible portion substantially at the center of the casing and having itsend portions hooked over the casing ends, shallow longitudinal channelsbeing formed on the outer surfaces of the tubular casing in whichchannels the end portions of the fusible link fit closely, and end capsfor the tubular casing constituting electrical terminals and grippingthe fuse ends in said channels between the outside surface of thesidewall of the tube and the inside surfaces of the sidewall of the endcaps to form electrical contact with the fuse ends.

3. A renewable cartridge fuse, as defined in claim 1,. wherein oneextreme end of the fuse link extends beyond the end cap and is exposedto view whereby a fuse designation on the end of the fuse linkis-exposed to view;

4. In a renewable cartridge fuse having, in combination, a tubularcasing with an externally screw-threaded ferrule on each end, twotubular metal members each having an internal thread to. engage saidferrules, and through the casing a fuse link. each end portion thereofbeing an electrical terminal thereof; means to electrically connect saidterminals, comprising, a multiple of transverse ridges formed on saidterminals to substantially correspond with said external threads of theferrules, said ferrules having a longitudinal groove provided in eachferrule by reducing said external threads of the ferrules sufiicientlyto contain said ridged terminals of the link hooked therein incomplementary relation with the threads, and said metal members screwedon the ferrules thereby forming a gripping connection with saidterminals of the link.

5. In a renewable cartridge fuse of the character described having, incombination, a tubular casing which includes two externally threadedferrules each fixed to an end of the casing, two tubular metal closurecaps each having an interna1 screw thread to engage the ferrules, and afuse lin keach end portion thereof being an elec-- trical *I'er minalthereof; means to electrically connect said link, comprising said capsand an internal conical surface formed-on the inside wall of each capadjacent to the internal threadthereof, said ferrules and an externalconical surface formed on the outside of each ferrule to correspond tosaid conical surface oftthe caps, and each of said ferrules alsoprovidedwith a longitudinal groove by reducing said external screw threadsumciently to contain a terminal of said link hooked against saidexternal conical surface and into said groove in combination with saidcaps, each cap closing an end of the casing, and gripping a portion of aterminal of the link between said corresponding conical surfaces, aportion of each terminal being also tripp d in the groove by theinternal screw threads of said p 6. In a renewable cartridge fusehaving, in combination, a tubularca'singwith an externally threadedferrule on each end, two tubular metal members each havingan internalscrew thread to engage the ferrules, and through the casing a fuse linkeach end portion thereof being an electrical terminal; means toelectrically connect said fuse link, comprising, said metal member. andblunt edges formed on the internal screw threads thereof, said ferrulesand a groove pro vided longitudinally in each ferrule by reducing theexternal threads thereof sufficiently to form serrations correspondingwith the threads, and

space to contain said terminals of the link hooked thereinincombiriation with said tubular members screwed on said ferrules, saidblunt edged threads of the members thereby contributing to said space atthe groove for the terminals and also deforming and gripping saidterminals against said serrations and in complementary relation to thethreads;

7. In a renewable cartridge fuse having, in combination, a tubularcasing, two externally screw threaded ferrules each fixed to an end ofthe casing, two tubular metal members each having an internal screwthread to engage the ferrules, and through the casing a fuse link eachend portion thereof being an electrical terminal thereof; means toelectrically connect said link, comprising, said tubular members and aconical formation provided on the internal side wall ad- Jacent to andtapering from the internal thread, also blunt edges formed on saidinternal threads, said ferrules and a cone frustum formed externally oneach ferrule to correspond with said conical formations of the tubularmembers, and each ferrule also provided with a longitudinal groove byreducing said external thread sufficiently to form serrationscorresponding therewith and space to contain said terminal of the linkwhen hooked against said frustum and into said grooves with said tubularmembers screwed on said ferrules, whereby portions of said terminals ofthe link are gripped between said frustums and said conical formationswith said grooves holding the terminals in position. and said bluntedged threads contribute to said grooves and space for said terminals,and also deform and grip said terminals on said serrations incomplementary relation with said threads.

8. In a renewable cartridge fuse having, in combination, a tubularcasing which includes two externally screw threaded ferrules each fixedto an end of the casing, two tubular metal members having internal screwthreads to engage the ferrules, and through the casing a fuse link eachend portion thereof being an electrical terminal thereof; means providedin said elements to elecmeans to interlock said elements when assembled,and means to vent said casing when the I fuse link blows, said meanscomprising, said tubular members and blunt edges provided on theinternal threads thereof, also an indentation provided in the rim ofeach tubular member, said ferrules and parallel channels formedlongitudinally in each ferrule by reducing the external threads, one ofsaid channels having an and open to the interior of said casing and theopposite end blocked, another of said channels having an end open to theexterior and the opposite end blocked, the hollows between said externalthreads forming lateral channels connecting said parallel channels, andeach of said ferrules also provided with a longitudinal groove byreducing the external thread thereof sufilciently to form serrations andspace to substantially contain said of the link hooked throughout saidsroovewith said tubular members screwed on said ferrules, thereby, saidblunt edged threads contribute. to said space in the groove for the,terminals and also deform and grip said terminals against saidserrations and in complementary relation to said threads, saidindentation in each tubular member engages with a bent up end of saidterminal to interlock all, said tubular members also complete theformation of said channels into a tortuous passage to vent gas, whichincludes a multiple of lateral gas passages of flame restrictingdiameter formed by said blunt edged threads incompletely filling saidhollows of the external screw threads, connecting the longitudinalchannels.

9. In a renewable cartridge fuse having, in combination, a fuse linkeach end portion thereof being an electrical terminal, a casingconsisting of a tube having two externally screw threaded ferrules eachfixed toan end of the tube, and'two tubular metal closure caps eachhaving an internal screw thread to engage the ferrules;

means to electrically connect said terminals of I the link, alsomeans tointerlock said elements when assembled, and means to vent expanding gas,comprising, said terminals anda multiple of transverse ridges formed ona portion of each terminal to substantially correspond with said threadsof the ferrules, said caps and blunt edges provided on said internalscrew thread of each cap, also an'internal conical surface formed on theinside wall at the closed end of each cap, and anindentation provided inthe rim of each cap, said ferrules and an external conical surfaceprovided on the end of each ferrule to correspond to said conicalsurface in the caps, also parallel vent channels formed longitudinallyin each ferrule by reducing the external threads, one of said channelshaving an end open to the interior of the .casing and the opposite endblocked, another of said external threads forming lateral channelsconnecting said parallel channels, and each ferrule also provided with alongitudinal groove formed by reducing said external thread sufficientlyto form serrations which correspond with the threads, and space tocontain a terminal of said link hooked against said external conicalsurface and throughout said groove with said caps screwed on theferrules, thereby; said caps close the casing; and electrically connectsaid terminals by gripping portions thereof between said correspondingconical surfaces, with said blunt'edged threads of the caps, which alsocontribute to said space in the grooves for the ridged portion of saidterminal, also gripping said ridged portions of the terminals againstsaid serrations and in complementary relation to said threads; said capsalso form said channels into a tortuous vent passage for gas, whichincludes a multiple of lateral passages of flame restricting diameterformed by said blunt edged threads incompletely filling the hollowsbetween said threads of the ferrules; and an end portion of eachterminal of the link bent up from the groove engages said indentationsof the caps to interlock all.

10..In a renewable cartridge fuse having, in combination, a fuse link, acasing therefore provided with an opening and screw threads adjacent theopening to engage a closure member for the opening, a closure member forthe opening having screw threads to engage the threads of the casing,and means to promptly vent expanded gas from said casing when a fusetherein blows; said means comprising, one of said parts and blunt edgesprovided on the screw threads thereof, the other of said parts andparallel channels formed longitudinally and across the screw threadsthereof, one of said channels having'an end open to the interior of saidcasing and the opposite end'blocked, another of said channels having anend open to the exterior of said casing and the.

opposite end blocked, said parts screwed together thereby forming amultiple of lateral gas passages of flame restricting diameter, by saidblunt edged threads incompletely filling the hollows between thecooperating threads, said lateral passages being preceded by arelatively larger passage from the interior of said casing and succeededby another relatively larger passage to the exterior, whereby expandinggas may be "copiously vented and are conducting vapor promptly dispersedwhen the fuse blows.

11. In a renewable cartridge fuse having, in combination, a tubularcasing, two externally screw threaded metal ferrules each attached to anend of the casing, and two tubular metal terminal members each having aninternal screw thread to engage said ferrules; means to promptly ventexpanded gas from the casing without the exit of fiame when said linkblows, comprising,

said tubular members and blunt edges formed on the internal screwthreads thereof, said ferrules and parallel channels formedlongitudinally in each ferrule oy reducing the external screw threadsthereof, one of said channels having an end open to the interior of saidcasing and the opposite end blocked, another of said channels having anend open to the exterior of the casing and the opposite endblocked, thehollows between the external threads of the ferrules forming lateralchannels connecting said longitudinal channels, and said tubular membersscrewed on said ferrules, thereby covering all channels and forming apassage for promptly venting gas, part of the passage including amultiple of gas passages of flame restricting diameter formed by saidblunt edged internal threads incompletely filling the hollows betweensaid external threads of the ferrules.

12. In a renewable cartridge fuse having, *in combination, a fusibleelement with an end portion, a casing for the fusible element, thecasing being provided with means to rotatably engage a terminal member,a terminal member adapted to rotatably engage said casing, one of saidparts of the casing being provided'with means to expose said end portionof the fusible element on the exteriorof the cartridge, and, anindentation provided in the cooperating part, to engage said end portionof the fusible element and thereby interlock said elements.

13. In a renewable cartridge fuse having, in combination, anonconducting casing having at each end an externally screw threadedferrule, each of said ferrule provided .with longitudinal groove, a fuselink through the casing with ends thereof hooked throughout saidgrooves, and internally screw threaded tubular terminals engaging saidferrule, each of said tubular terminal members provided with anindentation in the rim thereof to engage with portions of said ends ofthe link bent from the grooves to interlock said elements and keep thefuse assembled.

FRANKLIN S. KLEIN.

